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Office of National Marine Sanctuaries Office of Response and Restoration
Screening Level Risk Assessment Package
Alcoa Puritan
March 2013
National Oceanic and Atmospheric Administration Office of National Marine Sanctuaries Daniel J. Basta, Director Lisa Symons John Wagner Office of Response and Restoration Dave Westerholm, Director Debbie Payton Doug Helton Photo: Photograph of Alcoa Puritan
Source: Library of Contemporary History, Stuttgart (Retrieved from: http://www.uboat.net/allies/merchants/ships/1611.html)
i
Table of Contents
Project Background .......................................................................................................................................ii
Executive Summary ......................................................................................................................................1
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET) .....................................................................................................2
Vessel Particulars .........................................................................................................................................2 Casualty Information .....................................................................................................................................3 Wreck Location .............................................................................................................................................4 Casualty Narrative ........................................................................................................................................4 General Notes ..............................................................................................................................................5 Wreck Condition/Salvage History ................................................................................................................5 Archaeological Assessment .........................................................................................................................6 Assessment ..................................................................................................................................................7 Background Information References ............................................................................................................8 Vessel Risk Factors ......................................................................................................................................9
Section 2: Environmental Impact Modeling ...............................................................................................15
Release Scenarios Used in the Modeling ...................................................................................................15 Oil Type for Release ...................................................................................................................................17 Oil Thickness Thresholds ............................................................................................................................17 Potential Impacts to the Water Column .......................................................................................................18 Potential Water Surface Slick ......................................................................................................................19 Potential Shoreline Impacts.........................................................................................................................21
Section 3: Ecological Resources At Risk ..................................................................................................22
Ecological Risk Factors ...............................................................................................................................25
Section 4: Socio-Economic Resources At Risk ........................................................................................30
Socio-Economic Risk Factors .....................................................................................................................33
Section 5: Overall Risk Assessment and Recommendations for Assessment,
Monitoring, or Remediation ..........................................................................................................38
ii
Project Background The past century of commerce and warfare has left a legacy of thousands of sunken vessels along the U.S.
coast. Many of these wrecks pose environmental threats because of the hazardous nature of their cargoes,
presence of munitions, or bunker fuel oils left onboard. As these wrecks corrode and decay, they may
release oil or hazardous materials. Although a few vessels, such as USS Arizona in Hawaii, are well-
publicized environmental threats, most wrecks, unless they pose an immediate pollution threat or impede
navigation, are left alone and are largely forgotten until they begin to leak.
In order to narrow down the potential sites for inclusion into regional and area contingency plans, in
2010, Congress appropriated $1 million to identify the most ecologically and economically significant
potentially polluting wrecks in U.S. waters. This project supports the U.S. Coast Guard and the Regional
Response Teams as well as NOAA in prioritizing threats to coastal resources while at the same time
assessing the historical and cultural significance of these nonrenewable cultural resources.
The potential polluting shipwrecks were identified through searching a broad variety of historical sources.
NOAA then worked with Research Planning, Inc., RPS ASA, and Environmental Research Consulting to
conduct the modeling forecasts, and the ecological and environmental resources at risk assessments.
Initial evaluations of shipwrecks located within American waters found that approximately 600-1,000
wrecks could pose a substantial pollution threat based on their age, type and size. This includes vessels
sunk after 1891 (when vessels began being converted to use oil as fuel), vessels built of steel or other
durable material (wooden vessels have likely deteriorated), cargo vessels over 1,000 gross tons (smaller
vessels would have limited cargo or bunker capacity), and any tank vessel.
Additional ongoing research has revealed that 87 wrecks pose a potential pollution threat due to the
violent nature in which some ships sank and the structural reduction and demolition of those that were
navigational hazards. To further screen and prioritize these vessels, risk factors and scores have been
applied to elements such as the amount of oil that could be on board and the potential ecological or
environmental impact.
1
Executive Summary: Alcoa Puritan
The freighter Alcoa Puritan, torpedoed
and sunk during World War II off the
mouth of the Mississippi River in 1942,
was identified as a potential pollution
threat, thus a screening-level risk
assessment was conducted. The
different sections of this document
summarize what is known about the
Alcoa Puritan, the results of
environmental impact modeling
composed of different release
scenarios, the ecological and socio-
economic resources that would be at
risk in the event of releases, the
screening-level risk scoring results and overall risk assessment, and recommendations for assessment,
monitoring, or remediation.
Based on this screening-level assessment, each
vessel was assigned a summary score calculated
using the seven risk criteria described in this
report. For the Worst Case Discharge, Alcoa
Puritan scores Medium with 12 points; for the
Most Probable Discharge (10% of the Worse Case
volume), Alcoa Puritan scores Low with 11 points.
Given these scores, and the higher level of data
certainty, NOAA that general notations are made
in the Area Contingency Plans so that if a mystery
spill is reported in the general area, this vessel
could be investigated as a source, and that the
vessel be considered for an assessment if the
resources at risk are underrepresented in this
assessment. Archaeologists with BOEM and BSEE
could be contacted for more information based on
their surveys of the wreck site. Outreach efforts
with commercial and recreational fishermen who
frequent the area would be helpful to gain
awareness of localized spills in the site.
Vessel Risk Factors Risk Score
Pollution Potential Factors
A1: Oil Volume (total bbl)
Med
A2: Oil Type
B: Wreck Clearance
C1: Burning of the Ship
C2: Oil on Water
D1: Nature of Casualty
D2: Structural Breakup
Archaeological Assessment
Archaeological Assessment Not Scored
Operational Factors
Wreck Orientation
Not Scored
Depth
Confirmation of Site Condition
Other Hazardous Materials
Munitions Onboard
Gravesite (Civilian/Military)
Historical Protection Eligibility
WCD MP (10%)
Ecological Resources
3A: Water Column Resources Low Low
3B: Water Surface Resources Med Med
3C: Shore Resources Med Low
Socio-Economic Resources
4A: Water Column Resources Low Low
4B: Water Surface Resources Med Med
4C: Shore Resources Med Med
Summary Risk Scores 12 11
The determination of each risk factor is explained in the document.
This summary table is found on page 39.
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
2
SECTION 1: VESSEL BACKGROUND INFORMATION: REMEDIATION OF
UNDERWATER LEGACY ENVIRONMENTAL THREATS (RULET)
Vessel Particulars
Official Name: Alcoa Puritan
Official Number: 241003
Vessel Type: Freighter
Vessel Class: C1-B Cargo Ship
Former Names: N/A
Year Built: 1941
Builder: Bethlehem Steel Company, San Francisco, CA
Builder’s Hull Number: 5364
Flag: American
Owner at Loss: Alcoa Steamship Company
Controlled by: Unknown Chartered to: Unknown
Operated by: Unknown
Homeport: New York, NY
Length: 396 feet Beam: 60 feet Depth: 34 feet
Gross Tonnage: 6,759 Net Tonnage: 4,015
Hull Material: Steel Hull Fastenings: Riveted Powered by: Oil-fired steam
Bunker Type: Heavy Fuel Oil (Bunker C) Bunker Capacity (bbl): 9,103
Average Bunker Consumption (bbl) per 24 hours: Unknown
Liquid Cargo Capacity (bbl): 5,481 Dry Cargo Capacity: 447,748 cubic feet bale space
Tank or Hold Description: Vessel had five holds, the longest of which was 65' 3"
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
3
Casualty Information
Port Departed: Port of Spain, Trinidad Destination Port: Mobile, AL
Date Departed: Unknown Date Lost: May 6, 1942
Number of Days Sailing: Unknown Cause of Sinking: Act of War (Torpedoes and Shellfire)
Latitude (DD): 28.58357 Longitude (DD): -88.36667
Nautical Miles to Shore: 50 Nautical Miles to NMS: 315
Nautical Miles to MPA: 0 Nautical Miles to Fisheries: Unknown
Approximate Water Depth (Ft): 6,048 Bottom Type: Mud
Is There a Wreck at This Location? The listed location is probably not accurate but the wreck has been
located
Wreck Orientation: Resting on an even keel
Vessel Armament: None
Cargo Carried when Lost: 9,700 tons of Bauxite
Cargo Oil Carried (bbl): 0 Cargo Oil Type: None
Probable Fuel Oil Remaining (bbl): ≤ 9,103 Fuel Type: Heavy Fuel Oil (Bunker C)
Total Oil Carried (bbl): ≤ 9,103 Dangerous Cargo or Munitions: No
Munitions Carried: None
Demolished after Sinking: No Salvaged: No
Cargo Lost: Yes Reportedly Leaking: No
Historically Significant: Yes Gravesite: No
Salvage Owner: Not known if any
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
4
Wreck Location
Chart Number: 11360
Casualty Narrative
"At 18.55 hours on 6 May, 1942, a lookout on the unescorted and unarmed Alcoa Puritan (Master Yngvar
Axelstein Krantz) spotted a torpedo passing approximately 15 feet astern about 15 miles off the entrance
to the Mississippi River. The master immediately ordered full speed and swung the ship to keep the U-
boat dead astern to present as small a target as possible. U-507 surfaced and began to overtake the
freighter which was running at 16.5 knots. Five minutes the U-boat began to shell the ship from a distance
of one mile. In 40 minutes, about 75 rounds were fired, scoring about 50 hits and disabling the steering
gear. Two of the crew members suffered minor shrapnel injuries. The crew of ten officers, 37 crewmen
and seven passengers abandoned ship in one lifeboat and two rafts. At 19.43 hours, a torpedo was fired,
which struck below the #4 hatch and caused the ship to sink stern first in eight minutes. U-507 then
approached the survivors and a German officer with a megaphone shouted: Sorry we can´t help you -
hope you get ashore. And waved as the U-boat sailed away. All hands were picked up by the U.S. Coast
Guard cutter USS Boutwell (WPC 130) the same day and landed at Burrwood, Louisiana, after they had
been spotted by a patrol bomber. The passengers were repatriated seamen from the American steam
tanker T.C. McCobb, which was sunk by the Italian submarine Pietro Calvi (Olivieri) 600 miles off
British Guiana on 31 Mar, 1942."
-http://www.uboat.net:8080/allies/merchants/ships/1611.html
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
5
Under Yngvar Axelstein Krantz, the Alcoa Puritan was sunk by U-boat U-507, commanded by
Kapitanleutnant Harro Schacht, in the Gulf of Mexico. Schacht approached from starboard and fired with
both guns for about 40 minutes. The steering mechanism was disabled by one shot. With the vessel out of
control, the crew of the Alcoa Puritan abandoned ship. Schact then fired another torpedo into the ship and
it sank within 17 minutes.
-M. Wiggins "Torpedoes in the Gulf: Galveston and the U-Boats 1942-1943" Texas A&M University
Press, College Station (1995), 49-50.
The torpedoes damaged the ship's superstructure, perforated the funnel, broke all the windows and
instrument faces, set fire to parts of the interior, and finally disabled the steering mechanism at the stern.
This information was from Wikipedia and http://www.pastfoundation.org/DeepWrecks/AlcoaPuritan.htm.
-B.M. Browing Jr., "U.S. Merchant Vessel War Casualties of World War II", (Naval Institute Press,
1996), 96.
A Chicago Daily Tribune article in May 1942 records the sinking of three ships, two in the Gulf of
Mexico. Though no ship names are given, it is possibly describing the sinking of the Alcoa Puritan. If so,
it was recorded by a passenger that a torpedo was fired at the ship around noon, but it missed by 100 feet.
The ship then fled, but ten minutes later a large, and possibly new, German u-boat appeared and shelled
the fessel with 5" and 3" guns. One hit disabled the steering gear. After the ship was abandoned, the sub
fired a torpedo into the engine room and the ship sank rapidly.
-"SPEEDY U-BOATS BLAST 2 SHIPS IN GULF OF MEXICO" Chicago Daily Tribune (1872-1963);
May 10, 1942; ProQuest Historical Newspapers Chicago Tribune (1849 - 1986) pg. 2
General Notes
The Alcoa Puritan was launched in the West Basin of the Los Angeles Harbor from the Consolidated
Steel Corporation's Wilmington Shipyard.
-"FIVE SHIPS ARE LAUNCHED" New York Times (1857-Current file); Sep 28, 1942; ProQuest
Historical Newspapers The New York Times (1851 - 2005) pg. 10
Wreck Condition/Salvage History
“Between March and June 2001, about the same time as U-166’s discovery, Shell International
Exploration and Production contracted Fugro GeoServices Inc. (FGSI) to conduct a deep-tow survey for a
pipeline project. A large shipwreck was discovered on that survey in 1,965 m of water, 23 km southeast
of the Robert E. Lee and U-166 sites (Church et al., 2003). Marine archaeologist Laura Landry conducted
the archaeological assessment for the survey. Based on survey data and historical information, Landry
identified the wreck as Alcoa Puritan (USDI MMS, 2002). Shell International and Production Inc.
conducted the first ROV investigation of the wreck site on July 3, 2002. The ship’s name “ALCOA
PURITAN” and homeport “NEW YORK” were observed across the stern. The ROV investigation
confirmed the site’s identity and provided valuable data for researchers (Church et al., 2003). The 2004
research team investigated Alcoa Puritan on August 9 and 10, 2004.
The vessel lies in 1,964 m of water with the bow pointing southeast and stern northwest. The bow stands
4.3 m proud of the ambient seafloor, higher than the stern. A seafloor depression around the stern
measures approximately 50 m across and 4 m deep. The stern is approximately 1.2 m lower than the
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
6
ambient seafloor outside the depression. ROV reconnaissance of the main structure showed that the hull is
mostly intact with moderate superstructure damage. Numerous shell holes are visible along the hull.
Moderate damage was observed on the vessel’s starboard side, but the most extensive damage is to the
port side. A large hull breach caused by a torpedo is visible near the mud line, below the superstructure’s
aft portion. The tear measures 11.4 m across and extends 2.5 m above the mud line. Physical deterioration
is substantial in this area. Part of the aft bridge roof has collapsed, exposing the interior of the bridge; one
of the ship’s bridge telegraphs, lying on its side, is visible through the opening. The geophysical survey
data did not indicate an extensive debris field surrounding the wreck site. The observed debris was limited
and only four scattered artifacts were recorded around the hull.
The most notable artifact was one of U-507’s 105-mm shell casings, located approximately 112 m east of
Alcoa Puritan’s bow. Three transect survey lines run 300 m north of the vessel location revealed a large,
213-m by 213-m debris field containing large sections of wreckage, including a ship’s mast and telegraph.
The site had the greatest density of brown rusticles in the study, with 35% of the observable area covered.
The rusticle formations are similar to those observed at RMS Titanic. Multiple microbial test platforms
have been deployed since 1998 at Titanic and later analyzed (Cullimore and Johnston, 2000). Based on
available data, microbiologists developed a model projecting the Titanic’s rate of deterioration (Ballard,
2004). From these parallel rusticle investigations, an estimate of rusticle growth can be made for Alcoa
Puritan, where current rusticle development may be similar to that of Titanic during the mid-1970s when
it had been submerged for a similar length of time (Cullimore et al., 2001; Cullimore and Johnston, 2005).
Vertebrates and invertebrates observed at the site were similar to those observed at U-166 and Robert E.
Lee. Red deep-sea crabs (Chaceon quinquedens) were the predominant invertebrates collected, but a
hermit crab (Paragiopagurus sp.) also was collected. Numerous squat lobsters (Munidopsis sp.), Elaspodid
sea cucumbers, and a bright red carid shrimp (Notostomus sp.) were also observed.”
- http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/22_2/22.2_church.pdf
Archaeological Assessment
The archaeological assessment provides additional primary source based documentation about the sinking
of vessels. It also provides condition-based archaeological assessment of the wrecks when possible. It
does not provide a risk-based score or definitively assess the pollution risk or lack thereof from these
vessels, but includes additional information that could not be condensed into database form.
Where the current condition of a shipwreck is not known, data from other archaeological studies of
similar types of shipwrecks provide the means for brief explanations of what the shipwreck might look
like and specifically, whether it is thought there is sufficient structural integrity to retain oil. This is more
subjective than the Pollution Potential Tree and computer-generated resource at risk models, and as such
provides an additional viewpoint to examine risk assessments and assess the threat posed by these
shipwrecks. It also addresses questions of historical significance and the relevant historic preservation
laws and regulations that will govern on-site assessments.
In some cases where little additional historic information has been uncovered about the loss of a vessel,
archaeological assessments cannot be made with any degree of certainty and were not prepared. For
vessels with full archaeological assessments, NOAA archaeologists and contracted archivists have taken
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
7
photographs of primary source documents from the National Archives that can be made available for
future research or on-site activities.
Assessment
The freighter Alcoa Puritan was sunk by German Submarine U-507 off the coast of Louisiana on May 6,
1942. At the time of its loss, the ship was carrying 10,000 tons of bauxite and had a bunker capacity of
approximately 9,103 bbl of Bunker C fuel oil. As the ship travelled from Port of Spain, Trinidad destined
for Mobile, Alabama, it was overtaken by U-507, shelled, and struck by one torpedo (Fig. 1-1). According
to survivors, one torpedo was first seen to pass the freighter’s stern, causing the master to order full steam
and to begin to run from the unseen submarine. The submarine then came to the surface at full speed and
began to overtake Alcoa Puritan and fire shells at the freighter from a mile away. Over the course of 40
minutes, 50 shells fired by the submarine struck Alcoa Puritan, eventually destroying the freighter’s
steering gear and forcing the crew to abandon ship. Soon after the crew left the ship, the submarine came
up on the freighter’s port side and fired one torpedo, which struck Alcoa Puritan beneath the number four
hatch and caused the ship to sink by the stern within eight minutes.
Figure 1-1: U.S. Coast Guard diagram of the location of torpedo impact on Alcoa Puritan (Image courtesy of National
Archives, Washington, DC).
Based on the damage caused by the shellfire and the torpedo, it is possible that that the ship’s bunker
tanks were damaged or breached during the attack and may no longer contain oil. Since the ship was
travelling from Port of Spain, Trinidad to Mobile, Alabama, it is possible that much of the bunker oil had
been consumed before the ship sank. Today, the freighter is in 6,048 feet of water and rests on an even
keel, which is also an orientation that often leads to the loss of oil from vents and piping long before the
loss of structural integrity of hull plates from corrosion or other physical impacts.
Because NOAA archaeologists have never examined the site, we cannot provide additional condition
based assessments of the wreck, but archaeologists with the Bureau of Ocean Energy Management
(BOEM), Bureau of Safety and Environmental Enforcement (BSEE), and C & C Technologies, Inc. have
visited the site and can provide additional information to the U.S. Coast Guard if necessary. If the U.S.
Coast Guard decides to assess the wreck, it should first contact the archaeologists with BOEM and BSEE
for more information as well as to ensure compliance with archaeological standards for assessing a
historic resource.
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
8
It should also be noted that this vessel is of historic significance and will require appropriate actions be
taken under the National Historic Preservation Act (NHPA) and possibly the Sunken Military Craft Act
(SMCA) prior to any actions that could impact the integrity of the vessel. This vessel may be eligible for
listing on the National Register of Historic Places.
Background Information References
Vessel Image Sources: http://www.uboat.net/allies/merchants/ships/1611.html;
http://en.wikipedia.org/wiki/Alcoa_Puritan;
http://www.pastfoundation.org/DeepWrecks/AlcoaPuritan.htm;
http://drawings.usmaritimecommission.de/drawings_c1.htm
Construction Diagrams or Plans in RULET Database? Yes, for a C-1 B type cargo ship
Text References:
-B.M. Browing Jr., "U.S. Merchant Vessel War Casualties of World War II", (Naval Institute Press,
1996), 96, Wikipedia, http://www.pastfoundation.org/DeepWrecks/AlcoaPuritan.htm
-"FIVE SHIPS ARE LAUNCHED" New York Times (1857-Current file); Sep 28, 1942; ProQuest
Historical Newspapers The New York Times (1851 - 2005) pg. 10
-New York Times (1857-Current file); Nov 14, 1943; ProQuest Historical Newspapers The New York
Times (1851 - 2005) pg. 58
-"32 of Survivors of Two Vessels New Orleanians," The Times-Picayune, New Orleans, Sunday, 10 May
1942, page 12, column 4.
-Church, Robert, et al, "Archaeological and Biological Analysis of World War II Shipwrecks in the Gulf
of Mexico: Artificial Reef Effect in Deep Water,” U.S. Dept of the Interior, Minerals Management
Service, Gulf of Mexico OCS Region, New Orleans, OA, OCS Study MMS 2007-015, 387 pp.
-Church, Robert, et al, ""The SS Alcoa Puritan: Deepwater Discovery and Investigation, Proc of the
Underwater Intervention Conference, February, 2003.
-C. Hocking, ""Dictionary of Disasters at Sea During the Age of Steam: Including sailing ships and ships
of war lost in action 1824-1962"" (Lloyd's Register of Shipping, 1969), 20.
-Conwell, David M., Sea-Going Days, Part Two, privately distributed, Fairhope, Alabama, 1986, 73 pp.
-"The Alcoa Puritan," Society for Historical Archaeology Newsletter 35 (1): 24-25."
-AWOIS Database No. 253;
-CGD ID 5894;
-Global Wrecks Database NSS ID 574433;
-NIMA Database WK_Number 40169
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
9
Vessel Risk Factors
In this section, the risk factors that are associated with the vessel are defined and then applied to the Alcoa
Puritan based on the information available. These factors are reflected in the pollution potential risk
assessment development by the U.S. Coast Guard Salvage Engineering Response Team (SERT) as a
means to apply a salvage engineer’s perspective to the historical information gathered by NOAA. This
analysis reflected in Figure 1-2 is simple and straightforward and, in combination with the accompanying
archaeological assessment, provides a picture of the wreck that is as complete as possible based on
current knowledge and best professional judgment. This assessment does not take into consideration
operational constraints such as depth or unknown location, but rather attempts to provide a replicable and
objective screening of the historical date for each vessel. SERT reviewed the general historical
information available for the database as a whole and provided a stepwise analysis for an initial indication
of Low/Medium/High values for each vessel.
In some instances, nuances from the archaeological assessment may provide additional input that will
amend the score for Section 1. Where available, additional information that may have bearing on
operational considerations for any assessment or remediation activities is provided.
Each risk factor is characterized as High, Medium, or Low Risk or a category-appropriate equivalent such
as No, Unknown, Yes, or Yes Partially. The risk categories correlate to the decision points reflected in
Figure 1-2.
Each of the risk factors also has a “data quality modifier” that reflects the completeness and reliability of
the information on which the risk ranks were assigned. The quality of the information is evaluated with
respect to the factors required for a reasonable preliminary risk assessment. The data quality modifier
scale is:
High Data Quality: All or most pertinent information on wreck available to allow for thorough
risk assessment and evaluation. The data quality is high and confirmed.
Medium Data Quality: Much information on wreck available, but some key factor data are
missing or the data quality is questionable or not verified. Some additional research needed.
Low Data Quality: Significant issues exist with missing data on wreck that precludes making
preliminary risk assessment, and/or the data quality is suspect. Significant additional research
needed.
In the following sections, the definition of low, medium, and high for each risk factor is provided. Also,
the classification for the Alcoa Puritan is provided, both as text and as shading of the applicable degree of
risk bullet.
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
10
Pollution Potential Tree
Figure 1-2: U.S. Coast Guard Salvage Engineering Response Team (SERT) developed the above Pollution Potential Decision Tree.
Pollution Potential Factors
Risk Factor A1: Total Oil Volume
The oil volume classifications correspond to the U.S. Coast Guard spill classifications:
Low Volume: Minor Spill <240 bbl (10,000 gallons)
Medium Volume: Medium Spill ≥240 – 2,400 bbl (100,000 gallons)
High Volume: Major Spill ≥2,400 bbl (≥100,000 gallons)
Was there oil
onboard?
(Excel)
Was the wreck
demolished?
(Excel)
Yes or ?
Low Pollution Risk
No
Yes
Medium Pollution Risk
High Pollution Risk
No or ?
Was significant cargo
lost during casualty?
(Research)
Yes
Is cargo area
damaged?
(Research)
No or ?
No or ?
Yes
Likely all cargo lost?
(Research)
No or ?
Yes
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
11
The oil volume risk classifications refer to the volume of the most-likely Worst Case Discharge from the
vessel and are based on the amount of oil believed or confirmed to be on the vessel.
The Alcoa Puritan is ranked as High Volume because it is thought to have a potential for up to 9,103 bbl,
although some of that may have been lost at the time of the casualty or after the vessel sank. Data quality
is medium.
The risk factor for volume also incorporates any reports or anecdotal evidence of actual leakage from the
vessel or reports from divers of oil in the overheads, as opposed to potential leakage. This reflects the
history of the vessel’s leakage. There are no reports of leakage from the Alcoa Puritan.
Risk Factor A2: Oil Type
The oil type(s) on board the wreck are classified only with regard to persistence, using the U.S. Coast
Guard oil grouping1. (Toxicity is dealt with in the impact risk for the Resources at Risk classifications.)
The three oil classifications are:
Low Risk: Group I Oils – non-persistent oil (e.g., gasoline)
Medium Risk: Group II – III Oils – medium persistent oil (e.g., diesel, No. 2 fuel, light crude,
medium crude)
High Risk: Group IV – high persistent oil (e.g., heavy crude oil, No. 6 fuel oil, Bunker C)
The Alcoa Puritan is classified as High Risk because the bunker oil is heavy fuel oil, a Group IV oil type.
Data quality is high.
Was the wreck demolished?
Risk Factor B: Wreck Clearance
This risk factor addresses whether or not the vessel was historically reported to have been demolished as a
hazard to navigation or by other means such as depth charges or aerial bombs. This risk factor is based on
historic records and does not take into account what a wreck site currently looks like. The risk categories
are defined as:
Low Risk: The site was reported to have been entirely destroyed after the casualty
Medium Risk: The wreck was reported to have been partially cleared or demolished after the
casualty
High Risk: The wreck was not reported to have been cleared or demolished after the casualty
Unknown: It is not known whether or not the wreck was cleared or demolished at the time of or
after the casualty
The Alcoa Puritan is classified as High Risk because there are no known historic accounts of the wreck
being demolished as a hazard to navigation. Data quality is high.
1 Group I Oil or Nonpersistent oil is defined as “a petroleum-based oil that, at the time of shipment, consists of hydrocarbon fractions: At least 50% of which, by volume, distill at a temperature of 340°C (645°F); and at least 95% of which, by volume, distill at a temperature of 370°C (700°F).” Group II - Specific gravity less than 0.85 crude [API° >35.0] Group III - Specific gravity between 0.85 and less than .95 [API° ≤35.0 and >17.5] Group IV - Specific gravity between 0.95 to and including 1.0 [API° ≤17.5 and >10.0]
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
12
Was significant cargo or bunker lost during casualty?
Risk Factor C1: Burning of the Ship
This risk factor addresses any burning that is known to have occurred at the time of the vessel casualty
and may have resulted in oil products being consumed or breaks in the hull or tanks that would have
increased the potential for oil to escape from the shipwreck. The risk categories are:
Low Risk: Burned for multiple days
Medium Risk: Burned for several hours
High Risk: No burning reported at the time of the vessel casualty
Unknown: It is not known whether or not the vessel burned at the time of the casualty
The Alcoa Puritan is classified as High Risk because there are no known reports of fire at the time of the
casualty. Data quality is high.
Risk Factor C2: Reported Oil on the Water
This risk factor addresses reports of oil on the water at the time of the vessel casualty. The amount is
relative and based on the number of available reports of the casualty. Seldom are the reports from trained
observers so this is very subjective information. The risk categories are defined as:
Low Risk: Large amounts of oil reported on the water by multiple sources
Medium Risk: Moderate to little oil reported on the water during or after the sinking event
High Risk: No oil reported on the water
Unknown: It is not know whether or not there was oil on the water at the time of the casualty
The Alcoa Puritan is classified as High Risk because there are no known reports of oil spreading out
across the water as the vessel went down. Data quality is high.
Is the cargo area damaged?
Risk Factor D1: Nature of the Casualty
This risk factor addresses the means by which the vessel sank. The risk associated with each type of
casualty is determined by how violent the sinking event was and the factors that would contribute to
increased initial damage or destruction of the vessel (which would lower the risk of oil, other cargo, or
munitions remaining on board). The risk categories are:
Low Risk: Multiple torpedo detonations, multiple mines, severe explosion
Medium Risk: Single torpedo, shellfire, single mine, rupture of hull, breaking in half, grounding
on rocky shoreline
High Risk: Foul weather, grounding on soft bottom, collision
Unknown: The cause of the loss of the vessel is not known
The Alcoa Puritan is classified as Medium Risk because there was one torpedo detonation and
approximately 50 shells struck the ship. Data quality is high.
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
13
Risk Factor D2: Structural Breakup
This risk factor takes into account how many pieces the vessel broke into during the sinking event or
since sinking. This factor addresses how likely it is that multiple components of a ship were broken apart
including tanks, valves, and pipes. Experience has shown that even vessels broken in three large sections
can still have significant pollutants on board if the sections still have some structural integrity. The risk
categories are:
Low Risk: The vessel is broken into more than three pieces
Medium Risk: The vessel is broken into two-three pieces
High Risk: The vessel is not broken and remains as one contiguous piece
Unknown: It is currently not known whether or not the vessel broke apart at the time of loss or
after sinking
The Alcoa Puritan is classified as High Risk because it is not broken apart and remains in one contiguous
piece. Data quality is high.
Factors That May Impact Potential Operations
Orientation (degrees)
This factor addresses what may be known about the current orientation of the intact pieces of the wreck (with
emphasis on those pieces where tanks are located) on the seafloor. For example, if the vessel turtled, not only may
it have avoided demolition as a hazard to navigation, but it has a higher likelihood of retaining an oil cargo in the
non-vented and more structurally robust bottom of the hull.
The Alcoa Puritan is resting upright on the bottom. Data quality is high.
Depth
Depth information is provided where known. In many instances, depth will be an approximation based on
charted depths at the last known locations.
The Alcoa Puritan is 6,048 feet deep. Data quality is high.
Visual or Remote Sensing Confirmation of Site Condition
This factor takes into account what the physical status of the wreck site as confirmed by remote sensing or
other means such as ROV or diver observations and assesses its capability to retain a liquid cargo. This
assesses whether or not the vessel was confirmed as entirely demolished as a hazard to navigation, or
severely compromised by other means such as depth charges, aerial bombs, or structural collapse.
The location of the Alcoa Puritan has been surveyed by BOEM and C & C Technologies. Data quality is
high.
Other Hazardous (Non-Oil) Cargo on Board
This factor addresses hazardous cargo other than oil that may be on board the vessel and could potentially
be released, causing impacts to ecological and socio-economic resources at risk.
Section 1: Vessel Background Information: Remediation of Underwater Legacy Environmental Threats (RULET)
14
There are no reports of hazardous materials onboard. Data quality is high.
Munitions on Board
This factor addresses hazardous cargo other than oil that may be on board the vessel and could potentially
be released or detonated causing impacts to ecological and socio-economic resources at risk.
The Alcoa Puritan did not carry any munitions. Data quality is high.
Vessel Pollution Potential Summary
Table 1-1 summarizes the risk factor scores for the pollution potential and mitigating factors that would
reduce the pollution potential for the Alcoa Puritan. Operational factors are listed but do not have a risk
score.
Table 1-1: Summary matrix for the vessel risk factors for the Alcoa Puritan color-coded as red (high risk), yellow (medium risk), and green (low risk).
Vessel Risk Factors Data
Quality Score
Comments Risk
Score
Pollution Potential Factors
A1: Oil Volume (total bbl) Medium Maximum of 9,103 bbl, not reported to be leaking
Med
A2: Oil Type High Bunker oil is heavy fuel oil, a Group IV oil type
B: Wreck Clearance High Vessel not reported as cleared
C1: Burning of the Ship High No fire was reported
C2: Oil on Water High No oil was reported on the water
D1: Nature of Casualty High One torpedo detonation and shellfire
D2: Structural Breakup High Vessel remains in one contiguous piece
Archaeological Assessment
Archaeological Assessment High
Detailed sinking records and site reports of this
ship exist, assessment is believed to be very
accurate
Not Scored
Operational Factors
Wreck Orientation High Upright
Not Scored
Depth High 6,048 ft
Visual or Remote Sensing
Confirmation of Site Condition High Location has been surveyed
Other Hazardous Materials Onboard
High No
Munitions Onboard High No
Gravesite (Civilian/Military) High No
Historical Protection Eligibility (NHPA/SMCA)
High NHPA and possibly SMCA
Section 2: Environmental Impact Modeling
15
SECTION 2: ENVIRONMENTAL IMPACT MODELING
To help evaluate the potential transport and fates of releases from sunken wrecks, NOAA worked with
RPS ASA to run a series of generalized computer model simulations of potential oil releases. The results
are used to assess potential impacts to ecological and socio-economic resources, as described in Sections
3 and 4. The modeling results are useful for this screening-level risk assessment; however, it should be
noted that detailed site/vessel/and seasonally specific modeling would need to be conducted prior to any
intervention on a specific wreck.
Release Scenarios Used in the Modeling
The potential volume of leakage at any point in time will tend to follow a probability distribution. Most
discharges are likely to be relatively small, though there could be multiple such discharges. There is a
lower probability of larger discharges, though these scenarios would cause the greatest damage. A Worst
Case Discharge (WCD) would involve the release of all of the cargo oil and bunkers present on the
vessel. In the case of the Alcoa Puritan this would be about 10,000 bbl (rounded up from 9,103 bbl) based
on current estimates of the maximum amount of oil remaining onboard the wreck.
The likeliest scenario of oil release from most sunken wrecks, including the Alcoa Puritan, is a small,
episodic release that may be precipitated by disturbance of the vessel in storms. Each of these episodic
releases may cause impacts and require a response. Episodic releases are modeled using 1% of the WCD.
Another scenario is a very low chronic release, i.e., a relatively regular release of small amounts of oil
that causes continuous oiling and impacts over the course of a long period of time. This type of release
would likely be precipitated by corrosion of piping that allows oil to flow or bubble out at a slow, steady
rate. Chronic releases are modeled using 0.1% of the WCD.
The Most Probable scenario is premised on the release of all the oil from one tank. In the absence of
information on the number and condition of the cargo or fuel tanks for all the wrecks being assessed, this
scenario is modeled using 10% of the WCD. The Large scenario is loss of 50% of the WCD. The five
major types of releases are summarized in Table 2-1. The actual type of release that occurs will depend on
the condition of the vessel, time factors, and disturbances to the wreck. Note that episodic and chronic
release scenarios represent a small release that is repeated many times, potentially repeating the same
magnitude and type of impact(s) with each release. The actual impacts would depend on the
environmental factors such as real-time and forecast winds and currents during each release and the
types/quantities of ecological and socio-economic resources present.
The model results here are based on running the RPS ASA Spill Impact Model Application Package
(SIMAP) two hundred times for each of the five spill volumes shown in Table 2-1. The model randomly
selects the date of the release, and corresponding environmental, wind, and ocean current information
from a long-term wind and current database.
When a spill occurs, the trajectory, fate, and effects of the oil will depend on environmental variables,
such as the wind and current directions over the course of the oil release, as well as seasonal effects. The
Section 2: Environmental Impact Modeling
16
magnitude and nature of potential impacts to resources will also generally have a strong seasonal
component (e.g., timing of bird migrations, turtle nesting periods, fishing seasons, and tourism seasons).
Table 2-1: Potential oil release scenario types for the Alcoa Puritan.
Scenario Type Release per
Episode Time Period Release Rate
Relative Likelihood
Response Tier
Chronic (0.1% of WCD)
10 bbl Fairly regular intervals or constant
100 bbl over several days
More likely Tier 1
Episodic (1% of WCD)
100 bbl Irregular intervals Over several hours or days
Most Probable Tier 1-2
Most Probable (10% of WCD)
1,000 bbl One-time release Over several hours or days
Most Probable Tier 2
Large (50% of WCD)
5,000 bbl One-time release Over several hours or days
Less likely Tier 2-3
Worst Case 10,000 bbl One-time release Over several hours or days
Least likely Tier 3
The modeling results represent 200 simulations for each spill volume with variations in spill trajectory
based on winds and currents. The spectrum of the simulations gives a perspective on the variations in
likely impact scenarios. Some resources will be impacted in nearly all cases; some resources may not be
impacted unless the spill trajectory happens to go in that direction based on winds and currents at the time
of the release and in its aftermath.
For the large and WCD scenarios, the duration of the release was assumed to be 12 hours, envisioning a
storm scenario where the wreck is damaged or broken up, and the model simulations were run for a
period of 30 days. The releases were assumed to be from a depth between 2-3 meters above the sea floor,
using the information known about the wreck location and depth.
As discussed in the NOAA 2013 Risk Assessment for Potentially Polluting Wrecks in U.S. Waters,
NOAA identified 87 high and medium priority wrecks for screening-level risk assessment. Within the
available funds, it was not feasible to conduct computer model simulations of all 87 high and medium
priority wrecks. Therefore, efforts were made to create “clusters” of vessels in reasonable proximity and
with similar oil types. In general, the wreck with the largest potential amount of oil onboard was selected
for modeling of oil release volumes, and the results were used as surrogates for the other vessels in the
cluster. In particular, the regression curves created for the modeled wreck were used to determine the
impacts to water column, water surface, and shoreline resources. The Alcoa Puritan, with up to 10,000
bbl of heavy fuel onboard, was clustered with the R.W. Gallagher, which was modeled at 86,000 bbl of
heavy fuel oil. Figure 2-1 shows the location of both vessels.
It is important to acknowledge that these scenarios are only for this screening-level assessment. Detailed
site/vessel/and seasonally specific modeling would need to be conducted prior to any intervention on a
specific wreck.
Section 2: Environmental Impact Modeling
17
Figure 2-1: Location of the Alcoa Puritan (red triangle), the wreck discussed in this package, and the R.W. Gallagher
(red circle) which was the wreck that was actually modeled in the computer modeling simulations. The results for the R.W. Gallagher are used to estimate the impacts of releases from the Alcoa Puritan, as discussed in the text.
Oil Type for Release
The Alcoa Puritan contained a maximum of 10,000 bbl of heavy fuel oil (a Group IV oil). Thus, the spill
model for the R.W. Gallagher, which was run using heavy fuel oil, was used for this scoping assessment
of the Alcoa Puritan.
Oil Thickness Thresholds
The model results are reported for different oil thickness thresholds, based on the amount of oil on the
water surface or shoreline and the resources potentially at risk. Table 2-2 shows the terminology and
thicknesses used in this report, for both oil thickness on water and the shoreline. For oil on the water
surface, a thickness of 0.01 g/m2, which would appear as a barely visible sheen, was used as the threshold
for socio-economic impacts because often fishing is prohibited in areas with any visible oil, to prevent
contamination of fishing gear and catch. A thickness of 10 g/m2 was used as the threshold for ecological
impacts, primarily due to impacts to birds, because that amount of oil has been observed to be enough to
mortally impact birds and other wildlife. In reality, it is very unlikely that oil would be evenly distributed
on the water surface. Spilled oil is always distributed patchily on the water surface in bands or tarballs
with clean water in between. So, Table 2-2a shows the number of tarballs per acre on the water surface
for these oil thickness thresholds, assuming that each tarball was a sphere that was 1 inch in diameter.
For oil stranded onshore, a thickness of 1 g/m2 was used as the threshold for socio-economic impacts
because that amount of oil would conservatively trigger the need for shoreline cleanup on amenity
Section 2: Environmental Impact Modeling
18
beaches. A thickness of 100 g/m2 was used as the threshold for ecological impacts based on a synthesis of
the literature showing that shoreline life has been affected by this degree of oiling.2 Because oil often
strands onshore as tarballs, Table 2-2a shows the number of tarballs per m2 on the shoreline for these oil
thickness thresholds, assuming that each tarball was a sphere that was 1 inch in diameter.
Table 2-2a: Oil thickness thresholds used in calculating area of water impacted. Refer to Sections 3 and 4 for explanations of the thresholds for ecological and socio-economic resource impacts.
Oil Description Sheen
Appearance Approximate Sheen
Thickness No. of 1 inch
Tarballs Threshold/Risk Factor
Oil Sheen Barely Visible 0.00001 mm 0.01 g/m2
~5-6 tarballs per acre
Socio-economic Impacts to Water Surface/Risk Factor 4B-1 and 2
Heavy Oil Sheen Dark Colors 0.01 mm 10 g/m2 ~5,000-6,000 tarballs per acre
Ecological Impacts to Water Surface/ Risk Factor 3B-1 and 2
Table 2-2b: Oil thickness thresholds used in calculating miles of shoreline impacted. Refer to Sections 3 and 4 for explanations of the thresholds for ecological and socio-economic resource impacts.
Oil Description Oil
Appearance Approximate Sheen
Thickness No. of 1 inch
Tarballs Threshold/Risk Factor
Oil Sheen/Tarballs Dull Colors 0.001 mm 1 g/m2 ~0.12-0.14 tarballs/m2
Socio-economic Impacts to Shoreline Users/Risk Factor 4C-1 and 2
Oil Slick/Tarballs Brown to Black 0.1 mm 100 g/m2 ~12-14 tarballs/m2 Ecological Impacts to Shoreline Habitats/Risk Factor 3C-1 and 2
Potential Impacts to the Water Column
Impacts to the water column from an oil release from the Alcoa Puritan will be determined by the volume
of leakage. Because oil from sunken vessels will be released at low pressures, the droplet sizes will be
large enough for the oil to float to the surface. Therefore, impacts to water column resources will result
from the natural dispersion of the floating oil slicks on the surface, which is limited to about the top 33
feet. The metric used for ranking impacts to the water column is the area of water surface in mi2 that has
been contaminated by 1 part per billion (ppb) oil to a depth of 33 feet. At 1 ppb, there are likely to be
impacts to sensitive organisms in the water column and potential tainting of seafood, so this concentration
is used as a screening threshold for both the ecological and socio-economic risk factors for water column
resource impacts. To assist planners in understanding the scale of potential impacts for different leakage
volumes, a regression curve was generated for the water column volume oiled using the five volume
scenarios, which is shown in Figure 2-2, which is the regression curve for the R.W. Gallagher. Using this
figure, the water column impacts can be estimated for any spill volume. On Figure 2-2, arrows are used to
indicate the where the WCD for the Alcoa Puritan plots on the curve and how the area of the water
column impact is determined.
2 French, D., M. Reed, K. Jayko, S. Feng, H. Rines, S. Pavignano, T. Isaji, S. Puckett, A. Keller, F. W. French III, D. Gifford, J. McCue, G. Brown, E. MacDonald, J. Quirk, S. Natzke, R. Bishop, M. Welsh, M. Phillips and B.S. Ingram, 1996. The CERCLA type A natural resource damage assessment model for coastal and marine environments (NRDAM/CME), Technical Documentation, Vol. I - V. Office of Environmental Policy and Compliance, U.S. Dept. Interior, Washington, DC.
Section 2: Environmental Impact Modeling
19
Figure 2-2: Regression curve for estimating the area of water column at or above 1 ppb aromatics impacted as a
function of spill volume for the Alcoa Puritan. This regression curve was generated for the R.W. Gallagher, which has the same oil type and similar volume of potential releases as the Alcoa Puritan. The arrows indicate where the WCD for the Alcoa Puritan falls on the curve and how the area of water column impact can be determined for any spill volume.
Potential Water Surface Slick
The slick size from an oil release is a function of the quantity released Alcoa Puritan. The estimated water
surface coverage by a fresh slick (the total water surface area “swept” by oil over time) for the various
scenarios is shown in Table 2-3, as the median result of the 200 model runs for the R.W. Gallagher then
using the regression curve shown in Figure 2-3 to calculate the values for the different release scenarios
for the Alcoa Puritan. Note that this is an estimate of total water surface affected over a 30-day period.
The slick will not be continuous but rather be broken and patchy. Surface expression is likely to be in the
form of sheens, tarballs, and streamers. In the model, the representative heavy fuel oil used for this
analysis spreads to a minimum thickness of approximately 975 g/m2, and the oil is not able to spread any
thinner, owing to its high viscosity. As a result, water surface oiling results are identical for the 0.01 and
10 g/m2 thresholds. The location, size, shape, and spread of the oil slick(s) from an oil release from the
Alcoa Puritan will depend on environmental conditions, including winds and currents, at the time of
release and in its aftermath. Refer to the risk assessment package for the R.W. Gallagher for maps (Figs.
2-2 and 2-3) showing the areas potentially affected by slicks using the Most Probable volume and the
socio-economic and ecological thresholds.
Section 2: Environmental Impact Modeling
20
Table 2-3: Estimated slick area swept on water for oil release scenarios from the Alcoa Puritan, based on the model results for the R.W. Gallagher.
Scenario Type Oil Volume (bbl)
Estimated Slick Area Swept Mean of All Models
0.01 g/m2 10 g/m2
Chronic 10 120 mi2 120 mi2
Episodic 100 410 mi2 410 mi2
Most Probable 1,000 1,400 mi2 1,400 mi2
Large 5,000 3,400 mi2 3,400 mi2
Worst Case Discharge 10,000 4,900 mi2 4,900 mi2
The actual area affected by a release will be determined by the volume of leakage, whether it is from one
or more tanks at a time. To assist planners in understanding the scale of potential impacts for different
leakage volumes, a regression curve was generated for the water surface area oiled using the five volume
scenarios for the R.W. Gallagher, which is shown in Figure 2-3 and referenced in Table 2-3. Using this
figure, the area of water surface with a barely visible sheen can be estimated for any spill volume from the
Alcoa Puritan.
Figure 2-3: Regression curve for estimating the amount of water surface oiling as a function of spill volume for the
Alcoa Puritan, showing both the ecological threshold of 10 g/m2 and socio-economic threshold of 0.01 g/m2, based on the model results for the R.W. Gallagher. The arrows indicate where the WCD for the Alcoa Puritan falls on the curve and how the area of water surface impact can be determined for any spill volume. The curves for each threshold are so similar that they plot on top of each other.
Section 2: Environmental Impact Modeling
21
Potential Shoreline Impacts
Based on these modeling results, shorelines at risk of oiling extend from the Chandeleur Islands to south
of the Rio Grande, into Mexico. (Refer to Figure 2-6 in the R.W. Gallagher package to see the probability
of oil stranding on the shoreline at concentrations that exceed the threshold of 1 g/m2, for the Most
Probable release). However, the specific areas that would be oiled will depend on the currents and winds
at the time of the oil release(s), as well as on the amount of oil released. Estimated miles of shoreline
oiling above the socio-economic threshold of 1 g/m2 and the ecological threshold of 100 g/m
2 by scenario
type are shown in Table 2-4.
Table 2-4: Estimated shoreline oiling from leakage from the Alcoa Puritan, based on the modeling results for the R.W. Gallagher.
Scenario Type Volume (bbl) Estimated Miles of Shoreline
Oiling Above 1 g/m2 Estimated Miles of Shoreline
Oiling Above 100 g/m2
Chronic 10 16 1
Episodic 100 21 3
Most Probable 1,000 29 7
Large 5,000 36 14
Worst Case Discharge 10,000 39 19
The actual shore length affected by a release will be determined by the volume of leakage and
environmental conditions during an actual release. To assist planners in scaling the potential impact for
different leakage volumes, a regression curve was generated for the total shoreline length oiled using the
five volume scenarios for the R.W. Gallagher, as detailed in Table 2-4 and shown in Figure 2-4. Using
this figure, the shore length oiled can be estimated for any spill volume from the Alcoa Puritan.
Figure 2-4: Regression curve for estimating the amount of shoreline oiling at different thresholds as a function of spill
volume for the Alcoa Puritan, based on the model results for the R.W. Gallagher. The arrows indicate where the WCD for the Alcoa Puritan falls on the curve and how the length of shoreline impact can be determined for any spill volume.
Section 3: Ecological Resources at Risk
22
SECTION 3: ECOLOGICAL RESOURCES AT RISK
Ecological resources at risk from a catastrophic release of oil from the Alcoa Puritan (Table 3-1) include
numerous guilds of birds, particularly those sensitive to surface oiling while rafting or plunge diving to
feed and are present in nearshore/offshore waters. Coastal marshes and barrier islands support large
number of nesting shorebirds and wading birds and provide foraging grounds for overwintering
shorebirds and waterfowl and migrating shorebirds and passerines. In addition, nearshore waters of the
Gulf support highly productive coastal fisheries for both finfish and invertebrates. Kemp’s ridley sea
turtles use coastal waters heavily to travel between nesting beaches in South Texas and Mexico and
foraging grounds near the Mississippi River Delta.
Table 3-1: Ecological resources at risk from a release of oil from the Alcoa Puritan. (FT = Federal threatened; FE = Federal endangered; ST = State threatened; SE = State endangered).
Species Group Species Subgroup and Geography Seasonal Presence
Coastal birds Louisiana bays are important habitat for wintering waterfowl, supporting densities of up to 900 birds per square mile
Raptors (American kestrel, northern harriers, red-tailed hawk, turkey vulture, Cooper’s hawk, osprey, bald eagle) can all be present in the coastal marshes
Half of North American population of mottled duck inhabits Louisiana
Ospreys present during winter Mottled duck nests Mar-Sep
Nesting and migratory hotspots
Chandeleur Islands *bp = breeding pairs, otherwise numbers are individual bird counts
Critical habitat for wintering piping plover (FT)
Most abundant nesters: brown pelican (1,642 bp), laughing gull, Caspian tern, black skimmer (575 bp), royal tern (1-9,000 bp), sandwich tern (<33,000 bp)
Redhead and lesser scaup are common
Stopover for migratory birds Mississippi Delta (Pass a Loutre State WMA, Delta NWR)
Nesting habitat for mottled duck (445), secretive marsh birds, wading birds and brown pelican (2-3,000 bp)
High densities of king rails in the marsh
Habitat for 100,000 wintering waterfowl, including canvasback (9,000), northern pintail (48,000), gadwall (36,000)
Wintering habitat for western sandpiper, least sandpiper and dunlin Barataria-Terrebonne Bays
Grand Isle State Park is important migratory bird and snowy plover stopover
High abundances of overwintering blue and green-winged teal, American wigeon, ring-necked duck, lesser scaup, mallard, gadwall, and geese
Piping plovers overwintering on Elmer’s Island, W Grand Terre, and Fourchon east (~50 total)
Nesting: Short-billed dowitcher (1,800), Wilson’s plover (176 bp), black skimmer (899), gull-billed tern (>100), Forster’s tern (600-900 bp), least tern (321 bp), little blue heron (2,690 bp, 7 colonies), white ibis (2,500), roseate spoonbill (125 bp)
Isle Dernieres and Timbalier Islands
Raccoon Island has extremely high abundance of brown pelican, Wilson’s plover, royal and sandwich tern, great, snowy and reddish egret, great blue and tricolored heron
Piping plover present Aug-May Wilson’s plover nests May-Aug Short-billed dowitcher present in winter Roseate spoonbill nests Mar-Jul Mottled duck nests Mar-Sep Egrets nest Feb-Jul Ibises nest Apr-Aug Herons nest Mar-Aug Gulls nest Apr-Jul Skimmers nest May-Sep; Terns nest Apr-Sep Migrating shorebirds present spring and fall Wintering waterfowl present Oct-Mar
Section 3: Ecological Resources at Risk
23
Species Group Species Subgroup and Geography Seasonal Presence
Important wintering piping plover (50-100), snowy plover (<100) habitat
Stopover for long-billed curlew, red knot, and other shorebirds
Emergency stopover for passerines
Nesting: black skimmer (500 bp), sandwich tern (2,600 bp), least tern (50 bp), brown pelican (6,600 bp), Wilson’s plover (150 bp)
Atchafalaya Delta
Very important for wintering waterfowl, wading birds, and black skimmer
Marsh and scrub habitats important for rails, cranes, gulls, shorebirds, terns
Chenier Plain
Shell Keys Isl. stopover for white pelicans (1,807), brown pelicans, terns, gulls
> 400k overwintering ducks and geese
Mottled duck (1,000-2,000) present
Nesting: Forster’s tern (800 bp), gull-billed tern (200 bp), black skimmer (400 bp), roseate spoonbill (200 bp)
Piping plover (30), long-billed dowitcher (6,000) habitat present Bolivar Flats
100,000s of birds
Resting and feeding location for migrating shorebirds (American avocet, American golden-plover, semipalmated plover, Wilson’s plover, piping plover, snowy plover).
Resident mottled duck
Breeding roseate spoonbills (50) Jigsaw Island
Nesting: American oystercatcher (5 bp), black skimmer (10 bp), laughing gull (50 bp), Caspian tern (6 bp), royal terns (600 bp), sandwich tern (300 bp), tricolored heron
Mustang Bayou Island – wading birds, black skimmer, gull-billed/royal terns nesting Sundown Island (West Matagorda) – 18 species of colonial nesting birds, including one of the largest colonies of reddish egret in Texas (15,000 bp)
Nesting laughing gull (3,000 bp), royal tern (4,000 bp), sandwich tern (600 bp), tricolored heron (200 bp), brown pelican (2,000 bp), black skimmes, gull-billed tern, Caspian tern, reddish egret, little blue heron, snowy egret, great blue heron, great egret, cattle egret, white ibis, roseate spoonbill (these are all in lesser concentrations than above)
Laguna Vista spoils
Nesting gull-billed tern, royal tern, sandwich tern (1,000s), reddish egret, black skimmer
Pelagic distribution Convergence zones (thermoclines and warm core eddies) are areas of high biodiversity and abundance. Bird assemblages change seasonally
Early summer - terns, storm-petrels and gulls common; jaegers and shearwaters less common; tropicbirds, sulids and frigatebirds rare
Mid-summer - black terns extremely common; band-rumped storm petrel, magnificent frigatebird, Audubon’s shearwater, sooty tern present
Late summer - high abundances of terns
Section 3: Ecological Resources at Risk
24
Species Group Species Subgroup and Geography Seasonal Presence
Fall - laughing gull, royal tern, Pomarine jaeger common
Fall/winter - skuas present
Winter - herring and laughing gulls common
Sea Turtles Nesting
Kemp’s ridley (FE, SE) high nest counts on North Padre Island (~100 nests/yr) and low (<25 nests/yr) from Galveston Bay to northern Mexico
Densities of nesting Kemp’s ridley sea turtles increase greatly (100s-1,000s per year) just south of the model extent; their major nesting ground is at Rancho Nuevo, Mexico
Loggerheads (FT, ST) nest on the Chandeleur Islands and coastal Texas in low abundance
Greens (FT, ST) nest on beaches north to North Padre Island in low numbers
Hawksbill (FE, SE) and leatherback (FE, SE) nesting can occur on Padre Island National Seashore but is extremely rare
Distribution
Coastal Louisiana is a major foraging ground for Kemp’s ridley
Sargassum is important habitat for juvenile sea turtles
South Texas and northern Mexico inshore waters are important foraging grounds for juvenile green sea turtles
Shelf waters are important adult habitat for loggerheads
Loggerheads nest May-Oct Kemp’s ridley and Green nest Mar-Jul, hatch Apr-Sep Leatherbacks and hawksbills nest during the summer
Reptiles Rockefeller State Wildlife Refuge/Game Preserve has highest alligator nesting density in U.S. Diamondback terrapins can be found along the gulf shoreline in the area of impact
Marine Mammals Bottlenose dolphins (35-45k): Common in coastal waters including rivers, bays, and sounds throughout potential spill area. High concentrations in coastal Louisiana, especially around inlets and passes Whales and dolphins are often associated with shelf edge features, convergence zones, and Sargassum mats Manatees can be present in low abundance in inland waters
Manatees present spring-fall
Terrestrial mammals
Northern river otter, mink, nutria and muskrat can all be present in marsh habitats
Fish Inshore distributions
Marsh habitats are extremely productive and support high biodiversity and abundance of resident estuarine fish
Estuarine areas important nursery grounds for many commercial species: red, mutton, gray, lane, dog, yellowtail snapper, goliath, red, gag, yellowfin grouper
Coastal nursery areas for blacktip sharks, spinner sharks, Atlantic sharpnose sharks, bull sharks, sandbar sharks in the region
Passes are often sites of fish spawning Common in state waters
Gulf sturgeon (FT), bull shark, blacktip shark, spinner shark, silky shark, sharpnose shark, red snapper, mullet, lane snapper, red drum, gray snapper, vermillion snapper, king and Spanish mackerel, gag grouper, spotted seatrout, cobia, greater amberjack, black drum, hardheaded catfish, tarpon
Offshore distributions
Surface-oriented fish include hammerhead sharks, tiger sharks, silky sharks, mako sharks, manta rays, eagle rays, cownose ray, tunas, billfish, molas
Whale shark hotspot near mouth of the Mississippi
Shark species pup spring-summer Bluefin tuna are present to spawn in the spring Estuarine dependent fish migrate offshore in the fall/winter to spawn; juveniles and adults use estuaries during the spring/summer Bluefin tuna spawn
Section 3: Ecological Resources at Risk
25
Species Group Species Subgroup and Geography Seasonal Presence
Bluefin tuna spawn in areas offshore of coastal Texas and Louisiana
Sargassum is important habitat for juvenile of some pelagic fish species (i.e., dolphinfish, jacks, and triggerfish)
offshore Apr-May
Invertebrates Significant shrimp fisheries occur for white shrimp, brown shrimp, blue crabs, gulf stone crabs and oysters in coastal areas
Spawning occurs offshore, larval and juvenile development occurs in estuarine waters
Female blue crabs move to deeper waters to spawn
Spawning: Brown shrimp Mar-Jul; White shrimp Apr-Nov; Blue crab peaks Aug-Sep; Oysters in late spring and early fall
Benthic habitats Submerged aquatic vegetation is critical to numerous species and can be found in bays and sounds south of Galveston Bay. Larger and more contiguous beds occur on the inland side of the Chandeleur Islands and south of Matagorda Bay
Year round
The Environmental Sensitivity Index (ESI) atlases for the potentially impacted coastal areas from a leak
from the Alcoa Puritan are generally available at each U.S. Coast Guard Sector. They can also be
downloaded at: http://response.restoration.noaa.gov/esi. These maps show detailed spatial information on
the distribution of sensitive shoreline habitats, biological resources, and human-use resources. The tables
on the back of the maps provide more detailed life-history information for each species and location. The
ESI atlases should be consulted to assess the potential environmental resources at risk for specific spill
scenarios. In addition, the Geographic Response Plans within the Area Contingency Plans prepared by the
Area Committee for each U.S. Coast Guard Sector have detailed information on the nearshore and
shoreline ecological resources at risk and should be consulted.
Ecological Risk Factors
Risk Factor 3: Impacts to Ecological Resources at Risk (EcoRAR)
Ecological resources include plants and animals (e.g., fish, birds, invertebrates, and mammals), as well as
the habitats in which they live. All impact factors are evaluated for both the Worst Case and the Most
Probable Discharge oil release from the wreck. Risk factors for ecological resources at risk (EcoRAR) are
divided into three categories:
Impacts to the water column and resources in the water column;
Impacts to the water surface and resources on the water surface; and
Impacts to the shoreline and resources on the shoreline.
The impacts from an oil release from the wreck would depend greatly on the direction in which the oil
slick moves, which would, in turn, depend on wind direction and currents at the time of and after the oil
release. Impacts are characterized in the risk analysis based on the likelihood of any measurable impact,
as well as the degree of impact that would be expected if there is an impact. The measure of the degree of
impact is based on the median case for which there is at least some impact. The median case is the
“middle case” – half of the cases with significant impacts have less impact than this case, and half have
more.
For each of the three ecological resources at risk categories, risk is defined as:
Section 3: Ecological Resources at Risk
26
The probability of oiling over a certain threshold (i.e., the likelihood that there will be an impact
to ecological resources over a certain minimal amount); and
The degree of oiling (the magnitude or amount of that impact).
As a reminder, the ecological impact thresholds are: 1 ppb aromatics for water column impacts; 10 g/m2
for water surface impacts; and 100 g/m2 for shoreline impacts.
In the following sections, the definition of low, medium, and high for each ecological risk factor is
provided. Also, the classification for the Alcoa Puritan is provided, both as text and as shading of the
applicable degree of risk bullet, for the WCD release of 10,000 bbl and a border around the Most
Probable release of 1,000 bbl. Please note: The probability of oiling cannot be determined using the
regression curves; probability can only be determined from the 200 model runs. Thus, the modeling
results and regression curves for the R.W. Gallagher are used to estimate the values used in the risk
scoring for the degree of oiling only.
Risk Factor 3A: Water Column Impacts to EcoRAR
Water column impacts occur beneath the water surface. The ecological resources at risk for water column
impacts are fish, marine mammals, and invertebrates (e.g., shellfish, and small organisms that are food for
larger organisms in the food chain). These organisms can be affected by toxic components in the oil. The
threshold for water column impact to ecological resources at risk is a dissolved aromatic hydrocarbons
concentration of 1 ppb (i.e., 1 part total dissolved aromatics per one billion parts water). Dissolved
aromatic hydrocarbons are the most toxic part of the oil. At this concentration and above, one would
expect impacts to organisms in the water column.
Risk Factor 3A-1: Water Column Probability of Oiling of EcoRAR (not scored)
This risk factor reflects the probability that at least 0.2 mi2 of the upper 33 feet of the water column would
be contaminated with a high enough concentration of oil to cause ecological impacts. The three risk
scores for water column oiling probability are:
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
Risk Factor 3A-2: Water Column Degree of Oiling of EcoRAR
The degree of oiling of the water column reflects the total volume of water that would be contaminated by
oil at a concentration high enough to cause impacts. The three categories of impact are:
Low Impact: impact on less than 0.2 mi2 of the upper 33 feet of the water column at the
threshold level
Medium Impact: impact on 0.2 to 200 mi2 of the upper 33 feet of the water column at the
threshold level
High Impact: impact on more than 200 mi2 of the upper 33 feet of the water column at the
threshold level
The Alcoa Puritan is classified as Low Risk for degree of oiling for water column ecological resources
for the WCD of 10,000 bbl because the mean volume of water contaminated in the model runs was 0 mi2
Section 3: Ecological Resources at Risk
27
of the upper 33 feet of the water column. For the Most Probable Discharge of 1,000 bbl, the Alcoa
Puritan is classified as Low Risk for degree of oiling because the mean volume of water contaminated
was 0 mi2 of the upper 33 feet of the water column.
Risk Factor 3B: Water Surface Impacts to EcoRAR
Ecological resources at risk at the water surface include surface feeding and diving sea birds, sea turtles,
and marine mammals. These organisms can be affected by the toxicity of the oil as well as from coating
with oil. The threshold for water surface oiling impact to ecological resources at risk is 10 g/m2 (10 grams
of floating oil per square meter of water surface). At this concentration and above, one would expect
impacts to birds and other animals that spend time on the water surface.
Risk Factor 3B-1: Water Surface Probability of Oiling of EcoRAR (not scored)
This risk factor reflects the probability that at least 1,000 mi2 of the water surface would be affected by
enough oil to cause impacts to ecological resources. The three risk scores for oiling are:
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
Risk Factor 3B-2: Water Surface Degree of Oiling of EcoRAR
The degree of oiling of the water surface reflects the total amount of oil that would affect the water
surface in the event of a discharge from the vessel. The three categories of impact are:
Low Impact: less than 1,000 mi2 of water surface impact at the threshold level
Medium Impact: 1,000 to 10,000 mi2 of water surface impact at the threshold level
High Impact: more than 10,000 mi2 of water surface impact at the threshold level
The Alcoa Puritan is classified as Medium Risk for degree of oiling for water surface ecological
resources for the WCD because the mean area of water contaminated in the model runs was 4,900 mi2. It
is also classified as Medium Risk for degree of oiling for the Most Probable Discharge because the mean
area of water contaminated was 1,400 mi2.
Risk Factor 3C: Shoreline Impacts to EcoRAR
The impacts to different types of shorelines vary based on their type and the organisms that live on them.
For the modeled wrecks, shorelines were weighted by their degree of sensitivity to oiling. Wetlands are
the most sensitive (weighted as “3” in the impact modeling), rocky and gravel shores are moderately
sensitive (weighted as “2”), and sand beaches (weighted as “1”) are the least sensitive to ecological
impacts of oil. In this risk analysis for the Alcoa Puritan, shorelines have NOT been weighted by their
degree of sensitivity to oiling because these data are available only for modeled vessels. Therefore, the
impacts are evaluated only on the total number of shoreline miles oiled as determined from the regression
curve.
Risk Factor 3C-1: Shoreline Probability of Oiling of EcoRAR (not scored)
This risk factor reflects the probability that the shoreline would be coated by enough oil to cause impacts
to shoreline organisms. The threshold for shoreline oiling impacts to ecological resources at risk is 100
g/m2 (i.e., 100 grams of oil per square meter of shoreline). The three risk scores for oiling are:
Section 3: Ecological Resources at Risk
28
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
Risk Factor 3C-2: Shoreline Degree of Oiling of EcoRAR
The degree of oiling of the shoreline reflects the length of shorelines oiled by at least 100 g/m2 in the
event of a discharge from the vessel. The three categories of impact are:
Low Impact: less than 10 miles of shoreline impacted at the threshold level
Medium Impact: 10 - 100 miles of shoreline impacted at the threshold level
High Impact: more than 100 miles of shoreline impacted at the threshold level
The Alcoa Puritan is classified as Medium Risk for degree of oiling for shoreline ecological resources for
the WCD because the mean length of shoreline contaminated in the model runs was 19 miles. It is
classified as Low Risk for the Most Probable Discharge because the mean length of shoreline
contaminated in the model runs was 7 miles.
Considering the modeled risk scores and the ecological resources at risk, the ecological risk from
potential releases of the WCD of 10,000 bbl of heavy fuel oil from the Alcoa Puritan is summarized as
listed below and indicated in the far-right column in Table 3-2:
Water column resources – Low, because of the very small volume of water column likely
affected
Water surface resources – Medium, because there are a large number of birds and sea turtles at
risk. It should be noted that oil on the surface will not be continuous but rather be broken and
patchy and in the form of sheens, tarballs, and streamers
Shoreline resources – Medium, because sensitive shoreline resources include wetlands which are
difficult to clean and under long-term decline, large bird nesting colonies, turtle nesting beaches,
nursery areas for many fish and shellfish, and wintering habitat for listed bird species
Table 3-2: Ecological risk factor scores for the Worst Case Discharge of 10,000 bbl of heavy fuel oil from the Alcoa Puritan.
Risk Factor Risk Score Explanation of Risk Score Final Score
3A-1: Water Column Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Low 3A-2: Water Column Degree EcoRAR Oiling
Low Medium High The mean volume of water contaminated above 1 ppb
was 0 mi2 of the upper 33 feet of the water column
3B-1: Water Surface Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 3B-2: Water Surface Degree EcoRAR Oiling
Low Medium High The mean area of water contaminated above 10 g/m2
was 4,900 mi2
3C-1: Shoreline Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 3C-2: Shoreline Degree EcoRAR Oiling
Low Medium High The length of shoreline contaminated by at least 100
g/m2 was 19 mi
Section 3: Ecological Resources at Risk
29
For the Most Probable Discharge of 1,000 bbl of heavy fuel oil, the ecological risk from potential releases
from the Alcoa Puritan is summarized as listed below and indicated in the far-right column in Table 3-3:
Water column resources – Low, because of the very small volume of water column likely
affected
Water surface resources – Medium, because the area affected is smaller, but there are still a large
number of birds and sea turtles at risk. It should be noted that oil on the surface will not be
continuous but rather be broken and patchy and in the form of sheens, tarballs, and streamers
Shoreline resources – Low, because of the fewer salt marshes at risk
Table 3-3: Ecological risk factor scores for the Most Probable Discharge of 1,000 bbl of heavy fuel oil from the Alcoa Puritan.
Risk Factor Risk Score Explanation of Risk Score Final Score
3A-1: Water Column Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Low 3A-2: Water Column Degree EcoRAR Oiling
Low Medium High The mean volume of water contaminated above 1 ppb
was 0 mi2 of the upper 33 feet of the water column
3B-1: Water Surface Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 3B-2: Water Surface Degree EcoRAR Oiling
Low Medium High The mean area of water contaminated above 10 g/m2
was 1,400 mi2
3C-1: Shoreline Probability EcoRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Low 3C-2: Shoreline Degree EcoRAR Oiling
Low Medium High The length of shoreline contaminated by at least 100
g/m2 was 7 mi
Section 4: Socio-economic Resources at Risk
30
SECTION 4: SOCIO-ECONOMIC RESOURCES AT RISK
In addition to natural resource impacts, spills from sunken wrecks have the potential to cause significant
social and economic impacts. Socio-economic resources potentially at risk from oiling are listed in Table
4-1 and shown in Figures 4-1 and 4-2. The potential economic impacts include disruption of coastal
economic activities such as commercial and recreational fishing, boating, vacationing, commercial
shipping, and other activities that may become claims following a spill.
Socio-economic resources in the areas potentially affected by a release from the Alcoa Puritan include
recreational beaches in Louisiana and Texas that are very highly utilized year-round, including during
spring and fall for shore fishing. Many areas along the entire potential spill zone are widely popular
seaside resorts and support recreational activities such as boating, diving, sightseeing, sailing, fishing, and
wildlife viewing. There are two national seashores and a number of state parks with heavily utilized
beaches.
A release could impact shipping lanes, which accommodate ports and offshore lightering areas in
Mississippi, Louisiana, and Texas with a total of 26,000 vessel port calls and over 1.5 billion tonnage
annually. Commercial fishing is economically important to the region. A release could impact fishing
fleets from Maryland to Florida where regional commercial landings for 2010 exceeded $508 million.
In addition to the ESI atlases, the Geographic Response Plans within the Area Contingency Plans
prepared by the Area Committee for each U.S. Coast Guard Sector have detailed information on
important socio-economic resources at risk.
Spill response costs for a release of oil from the Alcoa Puritan would be dependent on volume of oil
released and specific areas impacted. The specific shoreline impacts and spread of the oil would
determine the response required and the costs for that response.
Table 4-1: Socio-economic resources at risk from a release of oil from the Alcoa Puritan.
Resource Type Resource Name Economic Activities
National Seashores Padre Island National Seashore, TX Gulf Island National Seashore, LA
National seashores provide recreation for local and tourist populations while preserving and protecting the nation’s natural shoreline treasures. National seashores are coastal areas federally designated as being of natural and recreational significance as a preserved area.
National Wildlife Refuges
Delta NWR (LA) Shell Keys NWR (LA) Sabine NWR (TX) Texas Point NWR (TX) McFaddin NWR (TX) Anahuac NWR (TX) Brazoria NWR (TX) San Bernard NWR (TX) Big Boggy NWR (TX) Aransas NWR (TX)
National wildlife refuges in two states may be impacted. These federally-managed and protected lands provide refuges and conservation areas for sensitive species and habitats.
Section 4: Socio-economic Resources at Risk
31
Resource Type Resource Name Economic Activities
State Parks Grand Isle SP, LA Cypremort Point SP, LA Sea Rim SP, TX Galveston Island SP, TX Matagorda Island SP, TX Goose Island SP, TX Mustang Island SP, TX Point Isabel Lighthouse State Historic Park, TX Boca Chica SP, TX
Coastal state parks are significant recreational resources for the public (e.g., swimming, boating, recreational fishing, wildlife viewing, nature study, sports, dining, camping, and amusement parks). They provide income to the states. State parks in the states of Louisiana and Texas are potentially impacted.
Commercial Fishing A number of fishing fleets use the western Gulf of Mexico area and surrounding waters for commercial fishing purposes.
Aransas Pass-Rockport Total Landings (2010): $8.6M
Brownsville-Port Isabel Total Landings (2010): $52.5M
Cameron Total Landings (2010): $11.5M
Delacroix-Yscloskey Total Landings (2010): $11.7M
Delcambre Total Landings (2010): $20.7M
Dulac-Chauvin Total Landings (2010): $45.1M
Empire-Venice Total Landings (2010): $53.7M
Freeport Total Landings (2010): $9.2M
Galveston Total Landings (2010): $28.0M
Golden Meadow-Leeville Total Landings (2010): $21.9M
Grand Isle Total Landings (2010): $14.2M
Gulfport-Biloxi Total Landings (2010): $13.0M
Intracoastal City Total Landings (2010): $26.4M
Lafitte-Barataria Total Landings (2010): $20.4M
Morgan City-Berwick Total Landings (2010): $5.7M
Palacios Total Landings (2010): $31.9M
Pascagoula-Moss Point Total Landings (2010): $8.9M
Port Arthur Total Landings (2010): $47.4M
Ports There are a number of significant commercial ports in the western Gulf of Mexico that could potentially be impacted by spillage and spill response activities. The port call numbers below are for large vessels only. There are many more, smaller vessels (under 400 GRT) that also use these ports.
Port Arthur, TX 1,183 port calls annually
Freeport, TX 777 port calls annually
Galveston, TX 699 port calls annually
Houston, TX 6,698 port calls annually
Texas City, TX 1,167 port calls annually
Corpus Christi, TX 1,037 port calls annually
Lake Charles, LA 683 port calls annually
Galveston Lightering Area, TX 591 port calls annually
Pascagoula, MS 562 port calls annually
Nederland Terminal, TX 389 port calls annually
New Orleans, LA 5,544 port calls annually
Loop Terminal, LA 295 port calls annually
Southwest Pass Lightering Area, LA 249 port calls annually
Gulfport, MS 197 port calls annually
Ingleside, TX 193 port calls annually
Point Comfort, TX 184 port calls annually
South Sabine Point Lightering Area, TX 118 port calls annually
Brownsville, TX 74 port calls annually
Beaumont, TX 64 port calls annually
Freeport Lightering Area, TX 30 port calls annually
Corpus Christi Lightering Area, TX 26 port calls annually
Section 4: Socio-economic Resources at Risk
32
Resource Type Resource Name Economic Activities
Sabine Pass, TX 235 port calls annually
Port Arthur, TX 1,183 port calls annually
Figure 4-1: Tribal lands, ports, and commercial fishing fleets at risk from a release from the Alcoa Puritan. (Note that
there are no tribal lands at risk.)
Section 4: Socio-economic Resources at Risk
33
Figure 4-2: Beaches, coastal state parks, and Federal protected areas at risk from a release from the Alcoa Puritan.
Socio-Economic Risk Factors
Risk Factor 4: Impacts to Socio-economic Resources at Risk (SRAR)
Socio-economic resources at risk (SRAR) include potentially impacted resources that have some
economic value, including commercial and recreational fishing, tourist beaches, private property, etc. All
impact factors are evaluated for both the Worst Case and the Most Probable Discharge oil release from
the wreck. Risk factors for socio-economic resources at risk are divided into three categories:
Water Column: Impacts to the water column and to economic resources in the water column
(i.e., fish and invertebrates that have economic value);
Water Surface: Impacts to the water surface and resources on the water surface (i.e., boating and
commercial fishing); and
Shoreline: Impacts to the shoreline and resources on the shoreline (i.e., beaches, real property).
The impacts from an oil release from the wreck would depend greatly on the direction in which the oil
slick moves, which would, in turn, depend on wind direction and currents at the time of and after the oil
release. Impacts are characterized in the risk analysis based on the likelihood of any measurable impact,
as well as the degree of impact that would be expected if there were one. The measure of the degree of
impact is based on the median case for which there is at least some impact. The median case is the
“middle case” – half of the cases with significant impacts have less impact than this case, and half have
more.
Section 4: Socio-economic Resources at Risk
34
For each of the three socio-economic resources at risk categories, risk is classified with regard to:
The probability of oiling over a certain threshold (i.e., the likelihood that there will be exposure
to socio-economic resources over a certain minimal amount known to cause impacts); and
The degree of oiling (the magnitude or amount of that exposure over the threshold known to
cause impacts).
As a reminder, the socio-economic impact thresholds are: 1 ppb aromatics for water column impacts; 0.01
g/m2 for water surface impacts; and 1 g/m
2 for shoreline impacts.
In the following sections, the definition of low, medium, and high for each socio-economic risk factor is
provided. Also, in the text classification for the Alcoa Puritan, shading indicates the degree of risk for a
WCD release of 10,000 bbl and a border indicates degree of risk for the Most Probable Discharge release
of 1,000 bbl. Please note: The probability of oiling cannot be determined using the regression curves;
probability can only be determined from the 200 model runs. Thus, the modeling results and regression
curves for the R.W. Gallagher are used to estimate the values used in the risk scoring for the degree of
oiling only.
Risk Factor 4A-1: Water Column: Probability of Oiling of SRAR (not scored)
This risk factor reflects the probability that at least 0.2 mi2 of the upper 33 feet of the water column would
be contaminated with a high enough concentration of oil to cause socio-economic impacts. The threshold
for water column impact to socio-economic resources at risk is an oil concentration of 1 ppb (i.e., 1 part
oil per one billion parts water). At this concentration and above, one would expect impacts and potential
tainting to socio-economic resources (e.g., fish and shellfish) in the water column; this concentration is
used as a screening threshold for both the ecological and socio-economic risk factors.
The three risk scores for oiling are:
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
Risk Factor 4A-2: Water Column Degree of Oiling of SRAR
The degree of oiling of the water column reflects the total amount of oil that would affect the water
column in the event of a discharge from the vessel. The three categories of impact are:
Low Impact: impact on less than 0.2 mi2 of the upper 33 feet of the water column at the
threshold level
Medium Impact: impact on 0.2 to 200 mi2 of the upper 33 feet of the water column at the
threshold level
High Impact: impact on more than 200 mi2 of the upper 33 feet of the water column at the
threshold level
The Alcoa Puritan is classified as Low Risk for degree of oiling for water column socio-economic
resources for the WCD of 10,000 bbl because the mean volume of water contaminated in the model runs
was 0 mi2 of the upper 33 feet of the water column. For the Most Probable Discharge of 1,000 bbl, the
Section 4: Socio-economic Resources at Risk
35
Alcoa Puritan is classified as Low Risk for oiling degree because the mean volume of water contaminated
was 0 mi2 of the upper 33 feet of the water column.
Risk Factor 4B-1: Water Surface Probability of Oiling of SRAR (not scored)
This risk factor reflects the probability that at least 1,000 mi2 of the water surface would be affected by
enough oil to cause impacts to socio-economic resources. The three risk scores for oiling are:
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
The threshold level for water surface impacts to socio-economic resources at risk is 0.01 g/m2 (i.e., 0.01
grams of floating oil per square meter of water surface). At this concentration and above, one would
expect impacts to socio-economic resources on the water surface.
Risk Factor 4B-2: Water Surface Degree of Oiling of SRAR
The degree of oiling of the water surface reflects the total amount of oil that would affect the water
surface in the event of a discharge from the vessel. The three categories of impact are:
Low Impact: less than 1,000 mi2 of water surface impact at the threshold level
Medium Impact: 1,000 to 10,000 mi2 of water surface impact at the threshold level
High Impact: more than 10,000 mi2 of water surface impact at the threshold level
The Alcoa Puritan is classified as Medium Risk for degree of oiling for water surface socio-economic
resources for the WCD of 10,000 bbl because the mean area of water contaminated in the model runs was
4,900 mi2. The Alcoa Puritan is classified as Medium Risk for degree of oiling for water surface socio-
economic resources for the Most Probable Discharge because the mean area of water contaminated was
1,400 mi2.
Risk Factor 4C: Shoreline Impacts to SRAR
The impacts to different types of shorelines vary based on economic value. For the modeled wrecks,
shorelines have been weighted by their degree of sensitivity to oiling. Sand beaches are the most
economically valued shorelines (weighted as “3” in the impact analysis), rocky and gravel shores are
moderately valued (weighted as “2”), and wetlands are the least economically valued shorelines
(weighted as “1”). In this risk analysis for the Alcoa Puritan, shorelines have NOT been weighted by their
degree of sensitivity to oiling because these data are available only for modeled vessels. Therefore, the
impacts are evaluated only on the total number of shoreline miles oiled as determined from the regression
curve.
Risk Factor 4C-1: Shoreline Probability of Oiling of SRAR (not scored)
This risk factor reflects the probability that the shoreline would be coated by enough oil to cause impacts
to shoreline users. The threshold for impacts to shoreline SRAR is 1 g/m2 (i.e., 1 gram of oil per square
meter of shoreline). The three risk scores for oiling are:
Low Oiling Probability: Probability = <10%
Medium Oiling Probability: Probability = 10 – 50%
High Oiling Probability: Probability > 50%
Section 4: Socio-economic Resources at Risk
36
Risk Factor 4C-2: Shoreline Degree of Oiling of SRAR
The degree of oiling of the shoreline reflects the total amount of oil that would affect the shoreline in the
event of a discharge from the vessel. The three categories of impact are:
Low Impact: less than 10 miles of shoreline impacted at threshold level
Medium Impact: 10 - 100 miles of shoreline impacted at threshold level
High Impact: more than 100 miles of shoreline impacted at threshold level
The Alcoa Puritan is classified as Medium Risk for degree of oiling for shoreline socio-economic
resources for the WCD because the mean length of shoreline contaminated in the model runs was 39
miles. The Alcoa Puritan is classified as Medium Risk for degree of oiling for shoreline socio-economic
resources for the Most Probable Discharge because the mean length of shoreline contaminated was 29
miles.
Considering the modeled risk scores and the socio-economic resources at risk, the socio-economic risk
from potential releases of the WCD of 10,000 bbl of heavy fuel oil from the Alcoa Puritan is summarized
as listed below and indicated in the far-right column in Table 4-2:
Water column resources – Low, because there would be virtually no impact on the water column
Water surface resources – Medium, because there would be a moderate area of offshore surface
waters affected in shipping lanes. It should be noted that oil on the surface will not be continuous
but rather be broken and patchy and in the form of sheens, tarballs, and streamers
Shoreline resources – Medium, because a moderate length of high-value, sensitive shoreline
would be impacted
Table 4-2: Socio-economic risk factor ranks for the Worst Case Discharge of 10,000 bbl of heavy fuel oil from the Alcoa Puritan.
Risk Factor Risk Score Explanation of Risk Score Final Score
4A-1: Water Column Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Low 4A-2: Water Column Degree SRAR Oiling
Low Medium High The mean volume of water contaminated above 1 ppb
was 0 mi2 of the upper 33 feet of the water column
4B-1: Water Surface Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 4B-2: Water Surface Degree SRAR Oiling
Low Medium High The mean area of water contaminated above 0.01 g/m2
was 4,900 mi2
4C-1: Shoreline Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 4C-2: Shoreline Degree SRAR Oiling
Low Medium High The length of shoreline contaminated by at least 1 g/m2
was 39 mi
Section 4: Socio-economic Resources at Risk
37
For the Most Probable Discharge of 1,000 bbl, the socio-economic risk from potential releases of heavy
fuel oil from the Alcoa Puritan is summarized as listed below and indicated in the far-right column in
Table 4-3:
Water column resources – Low, because there would be virtually no impact on the water column
Water surface resources – Medium, because there would be a moderate area of offshore surface
waters affected in shipping lanes. It should be noted that oil on the surface will not be continuous
but rather be broken and patchy and in the form of sheens, tarballs, and streamers
Shoreline resources – Medium, because a moderate length of high-value, sensitive shoreline
would be impacted
Table 4-3: Socio-economic risk factor ranks for the Most Probable Discharge of 1,000 bbl of heavy fuel oil from the Alcoa Puritan.
Risk Factor Risk Score Explanation of Risk Score Final Score
4A-1: Water Column Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Low 4A-2: Water Column Degree SRAR Oiling
Low Medium High The mean volume of water contaminated above 1 ppb
was 0 mi2 of the upper 33 feet of the water column
4B-1: Water Surface Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 4B-2: Water Surface Degree SRAR Oiling
Low Medium High The mean area of water contaminated above 0.01 g/m2
was 1,400 mi2
4C-1: Shoreline Probability SRAR Oiling
Low Medium High N/A: Only available for modeled vessels
Med 4C-2: Shoreline Degree SRAR Oiling
Low Medium High The length of shoreline contaminated by at least 1 g/m2
was 29 mi
Section 5: Overall Risk Assessment and Recommendations for Assessment, Monitoring, or Remediation
38
SECTION 5: OVERALL RISK ASSESSMENT AND RECOMMENDATIONS
FOR ASSESSMENT, MONITORING, OR REMEDIATION
The overall risk assessment for the Alcoa Puritan is comprised of a compilation of several components
that reflect the best available knowledge about this particular site. Those components are reflected in the
previous sections of this document and are:
Vessel casualty information and how site formation processes have worked on this vessel
Ecological resources at risk
Socio-economic resources at risk
Other complicating factors (war graves, other hazardous cargo, etc.)
Table 5-1 summarizes the screening-level risk assessment scores for the different risk factors, as
discussed in the previous sections. As noted in Sections 3 and 4, each of the ecological and socio-
economic risk factors each has two components, probability and degree. Of those two, degree is given
more weight in deciding the combined score for an individual factor, e.g., a high probability and medium
degree score would result in a medium overall for that factor. Please note: The probability of oiling
cannot be determined using the regression curves; probability can only be determined from the 200 model
runs. Thus, the modeling results and regression curves for the R.W. Gallagher were used to estimate the
values used in the risk scoring for the degree of oiling only.
In order to make the scoring more uniform and replicable between wrecks, a value was assigned to each
of the 7 criteria. This assessment has a total of 7 criteria (based on table 5-1) with 3 possible scores for
each criteria (L, M, H). Each was assigned a point value of L=1, M=2, H=3. The total possible score is 21
points, and the minimum score is 7. The resulting category summaries are:
Low Priority 7-11
Medium Priority 12-14
High Priority 15-21
For the Worst Case Discharge, Alcoa Puritan scores Medium with 12 points; for the Most Probable
Discharge, Alcoa Puritan scores Low with 11 points. Under the National Contingency Plan, the U.S.
Coast Guard and the Regional Response Team have the primary authority and responsibility to plan,
prepare for, and respond to oil spills in U.S. waters. Based on the technical review of available
information, NOAA proposes the following recommendations for the Alcoa Puritan. Archaeologists with
BOEM and BSEE could be contacted for more information based on their surveys of the wreck site. The
final determination of what type of action, if any, rests with the U.S. Coast Guard.
Alcoa Puritan Possible NOAA Recommendations
Wreck should be considered for further assessment to determine the vessel condition, amount of oil onboard, and feasibility of oil removal action
Location is unknown; Use surveys of opportunity to attempt to locate this vessel and gather more information on the vessel condition
Conduct active monitoring to look for releases or changes in rates of releases
✓ Be noted in the Area Contingency Plans so that if a mystery spill is reported in the general area, this vessel could be investigated as a source
✓ Conduct outreach efforts with commercial and recreational fishermen who frequent the area, to gain awareness of changes in the site
Section 5: Overall Risk Assessment and Recommendations for Assessment, Monitoring, or Remediation
39
Table 5-1: Summary of risk factors for the Alcoa Puritan.
Vessel Risk Factors Data
Quality Score
Comments Risk
Score
Pollution Potential Factors
A1: Oil Volume (total bbl) Medium Maximum of 9,103 bbl, not reported to be leaking
Med
A2: Oil Type High Bunker oil is heavy fuel oil, a Group IV oil type
B: Wreck Clearance High Vessel not reported as cleared
C1: Burning of the Ship High No fire was reported
C2: Oil on Water High No oil was reported on the water
D1: Nature of Casualty High One torpedo detonation and shellfire
D2: Structural Breakup High Vessel remains in one contiguous piece
Archaeological Assessment Archaeological Assessment High
Detailed sinking records and site reports of this ship exist, assessment is believed to be very accurate
Not Scored
Operational Factors
Wreck Orientation High Upright
Not Scored
Depth High 6,048 ft
Visual or Remote Sensing Confirmation of Site Condition
High Location has been surveyed
Other Hazardous Materials Onboard
High No
Munitions Onboard High No
Gravesite (Civilian/Military) High No
Historical Protection Eligibility (NHPA/SMCA)
High NHPA and possibly SMCA
WCD Most
Probable
Ecological Resources
3A: Water Column Resources High Very little impact likely Low Low
3B: Water Surface Resources High
Heavy fuel oil forms persistent tarballs that can travel long distances posing risks to birds and sea turtles, esp. when concentrated in convergence zones and Sargassum
Med Med
3C: Shore Resources High Persistent tarballs can strand on beaches and marshes, fouling habitats and animals
Med Low
Socio-Economic Resources
4A: Water Column Resources High Virtually no impact on the water column Low Low
4B: Water Surface Resources High Moderate area of offshore surface waters affected in shipping lanes
Med Med
4C: Shore Resources High Moderate length of high-value, sensitive shoreline would be impacted
Med Med
Summary Risk Scores 12 11